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Description
The 5th generation cellular mobile networks uses precoding techniques to focus electromagnetic fields (EMFs) emitted by base stations at the user equipment (UE). In this work, this type of exposure, denoted as auto-induced downlink exposure, is studied. The exposure scenario consists of a UE positioned next to the skin. The working frequency is 26 GHz and the UE can have a parallel or orthogonal polarization to the skin. The model that is used is a multi-layered model, since the exposure is limited to the outer tissues at the working frequency. The EMFs are determined analytically and the focusing is achieved using MRT precoding. The field enhancement at and around the UE depends on the focusing distance and UE polarization. Focusing to a UE polarized parallel to the skin is not efficient up to a distance of 3 mm in comparison to an orthogonally polarized one. Interestingly, for larger separation distances, the best focusing is found for a UE polarized parallel to the skin. The exposure is quantified in terms of the peak spatial absorbed power density. For all considered distances, a lower exposure is found for a parallel polarization in comparison to orthogonal polarization. A periodic behaviour as a function of focusing distance is found for the absorbed power density and the power density at the UE.
